The present invention relates generally to a polydimethylsiloxane sheet, and more particularly to a polydimethylsiloxane sheet for the formation of a metal thin film and a metal pattern shaped as desired, an optical element having a plurality of nano-order metal patterns formed on a flexible resin substrate, and a manufacturing method thereof.
So far, polydimethylsiloxane (hereinafter often abbreviated as PDMS) sheets have been advantageously used in a variety of application fields inclusive of electronic and electric devices or the like because of excelling in heat resistance, cold resistance and weather resistance and having stabilized electric characteristics.
Optical elements having a diffraction grating formed on a glass substrate or the like have also been widely used so far in the art, and more recently, an optical element having a metal pattern formed on a flexible resin substrate has been proposed (the 56th Spring Meeting, 2009—The Japan Society of Applied Physics—by Oh Gyosei et. al. at University of Tsukuba, 1p-H-9). This optical element changes in the inter-metal pattern nano-order locations upon receipt of external force by the substrate, resulting in changes in the inter-metal pattern near-field interactions and, hence, optical responses. Another proposal has been made of an optical element having zero reflectivity at an interface with a substance without depending on the direction of polarization for 100% transmission of light (JP(A) 2006-350232). This optical element has a structure in which a plurality of magnetic resonators, each being a nano-structure wherein silver as a meta-material is C-shaped, are located on a glass substrate.
A problem with the conventional PDMS sheets, however, has been poor adhesion to metals. Another problem has been that when a PDMS sheet is placed on a silicon-containing substrate such as a glass substrate, a quartz substrate or a silicon substrate to form a metal thin film or a metal pattern of any desired shape thereon, or stored on that substrate over an extended period of time, it may stick to the substrate, making handleability and stability worse.
Being flexible and transparent to light, the PDMS sheet could also be used as a flexible resin substrate forming a part of such an optical element as set forth in the aforesaid non-patent publication. However, a problem with the direct formation of a metal pattern on the conventional PDMS sheet, however, has been that the metal pattern peels off and de-bonds due to repetitive application of external force on the PDMS sheet, because there is a weak adhesion power of the metal nano-structure to the PDMS sheet.